The present invention relates to the fields of pharmaceutical chemistry and synthetic organic chemistry. (R)—N-(3,4-Difluoro-2-(2-fluoro-4-iodophenylamino)-6-methoxyphenyl)-1-(2,3-dihydroxypropyl)cyclopropane-1-sulfonamide and (S)—N-(3,4-difluoro-2-(2-fluoro-4-iodophenylamino)-6-methoxyphenyl)-1-(2,3-dihydroxypropyl)cyclopropane-1-sulfonamide are known to possess inhibitory properties against MEK enzymes and are of therapeutic value (see US published patent application US 2008/0058340 A1). Described herein are methods for their preparation.